除虫菊 chu chong ju

Pyrethrum cinerariifolium Treviranus, Index Sem. Hort. Bot. Wratislav. App. 2: 2. 1820; Chrysanthemum cinerariifolium (Treviranus) Visiani.

Herbs, perennial; stems 17-60 cm tall, solitary or fascicled, unbranched or branched from base, pubescent with appressed T-shaped or furcate hairs. Basal leaves: petiole 10-20 cm; leaf blade ovate or elliptic, 1.5-4 × 1-2 cm, both surfaces silvery grayish, appressed pubescent with T-shaped and furcate hairs, 2-pinnatisect; primary segments 3-5-paired; ultimate segments linear or oblong-ovate, margin entire or few dentate. Lower and middle leaves similar, large, shortly petiolate. Capitula apically solitary or 3-10 in apical lax corymb. Involucre cup-shaped, 1.2-1.5 cm in diam.; phyllaries in 4 rows, abaxially pubescent especially in outer ones, outer ones lanceolate, ca. 4 mm, middle and inner ones lanceolate to broadly linear, 5-6 mm, margin narrowly white scarious. Ray florets white; lamina 1.2-1.5 cm, apex truncate or emarginate. Achenes 2.5-3.5 mm. Corona 0.8-1.5 mm, margin shallowly lobed. Fl. and fr. May-Aug. 2n = 18*, 24, 27, 29, 31, 34, 36.

Widely cultivated. Anhui, Guizhou, Hebei, Liaoning, Zhejiang [native to SE Europe; now widely cultivated].

Tanacetum cinerariifolium is widely cultivated, mainly in tropical upland regions, as a source of pyrethrins, which are extracted from the dried capitula and used as insecticides. Pyrethroids are important insecticides obtained by the chemical modification of pyrethrins.